I would complain to these guy's. Polaris don't care. I've tried before. It's a waste of time.

http://www.cpsc.gov/

 

When you bleed it do it with the cap off and keep it full while bleeding.After you get the air out be sure to keep the resivoir full at all times and you shouldnt have any more trouble.

 

It will still happen no matter how you bleed it. The master cyl. is a bad design. It leaks air into the seals. Take it from me, I use to be a old wrench from way back. Now I'm a mechanical engineer. Your going to have to deal with it or go with Fixitmatt solution. Or you can bitch about it and make Polaris recall it. It is a safety problem. Somebodys life can depend on it.

 

I think this a safety problem that needed to be delt with a long time ago. I'm glad this came up again. I'm going to send in my complaint today and I advise anyone else with the same problem to do the same thing. Someone need's to get the ball rolling to get this safety problem fixed. I'm sick of sinking money in this quad. Now it's Polaris's turn.

Just go to: http: www.cpsc.gov
And click on to: Report an Unsafe Product

 

Hello garrett5462. I would suggest you look at this thread.
Brake It is clear that no one seems to know what the problem is in all cases. Many quads rear brakes work just fine and others seem to have problems. I would not go out and buy a new master cylinder without checking the points listed on the above thread.
Bryce